LCD-based electronic devices such as Ultra Mobile PC (UMPC), laptops/PCs, personal digital assistants (PDAs), cellular phones, portable digital media players, and the like are becoming ubiquitous in modern technological societies. These devices offer specialized functionality in form factors small enough to carry in a pocket or some other small carrying bag. At least one reason why these types of devices are so popular is because display technology, which provides a convenient user interface, has advanced to a point where relatively small form factors are efficient and inexpensive. Indeed, even the most inexpensive portable electronic devices now include high frame rate color displays. However, conventional displays are not without some disadvantages.
Typically, a PDA may include a refresh-based, high frequency (REHF) display for displaying user selected information. One example of an REHF display is a liquid crystal display (LCD). LCDs have many desirable characteristics including high frame rates which provide for a satisfying visual experience when rapidly switching between screens or when scrolling across a screen. However, typical displays having high screen refresh rates may suffer from poor readability because backlights, which are required in those displays, may be adversely affected by ambient lighting conditions. Eye strain is commonly reported by users and has been documented in some medical literature. Users of UMPCs or PDAs are familiar with the poor readability of LCDs under bright light or direct sunlight. In some examples, shading the screen or moving to a darker environment may be necessary to read an LCD. In another embodiment, the REHF display comprises a mirasol display, which uses micro-electro-mechanical systems (MEMS) drive IMOD reflective technology, such as that provided by Qualcomm.
In order to overcome the shortcomings of an LCD, bistable, low frequency (BILF) displays may be utilized instead of an LCD. One example of a BILF display is and electronic paper display (EPD). EPDs utilize a material called electronic ink and are commercially available under the trade name E INK®. In another embodiment, the BILF display comprises a mirasol display, which uses micro-electro-mechanical systems (MEMS) drive IMOD reflective technology, such as that provided by Qualcomm. EPDs are ideally suited for flexible display applications due to their thin form factor and inherent flexibility. EPDs provide an image stable reflective display technology that uses ultra-low power but is easily read under any lighting condition including direct sunlight. In addition, EPDs provide a bistable display and unlike LCDs, an image on an EPD looks the same from all viewing angles. Further, EPDs will not distort when touched or flexed, making EPDs the ideal display medium for flexible displays and portable devices. EPDs however, cannot, in many examples, completely replace LCDs. At least one reason is because EPDs typically have a low frame rate. As noted above, conventional LCDs are typically configured with high frame rates, which may serve to enhance a user's viewing experience especially when rapidly scrolling through multiple displays. In addition, using a mouse requires high frame rates so that the mouse pointer appears to have smooth movement across a screen. Furthermore, currently, a majority of reading content is created for viewing with an REHL display application such as an LCD application while few applications are written for BILF displays such as an EPD. This trend is likely to continue. It may, therefore, be advantageous to easily display the output of existing REHF display applications on BILF displays such as an EPD.
It may, therefore, be desirable to provide a complementary display to conventional portable electronic device or desktop PC displays which provide a highly readable display that overcomes harsh ambient light conditions, reduces eye strains and does not overly diminish battery life. The method and the heterogeneous display hardware design can deliver many new classes of EPD usage models, including: (1) the capability to extend (or migrate) an REHF-based application to a BILF display for better reading experience where a user may also browse the pages on BILF display without changing the application (in this example, a BILF display could be tightly integrated with an REHF display through system bus or loosely linked through an external device); and (2) the ability to create dual-display aware applications that can take advantages of the unique benefits of both BILF and REHF displays at the same time. These methods can enable extreme ease-of-use involving two heterogeneous displays without traditional “file synch” model that requires multiple steps of selecting files, transfer files and then opening files and then browsing to the desired page. As such, methods for controlling complementary bistable and refresh-based displays are provided herein.